The function of the Chevrolet Blower Motor Resistor is to reduce the amount of voltage reaching the motor from the 12 volt system on your vehicle. The exact amount of resistance the blower motor resistor has is specified by the motor that is used on your Chevrolet system.
The replacement of the Chevrolet blower motor resistor is possible by anyone that can solder a connection and have the ability to read the resistor. Each blower motor resistor is covered with a color coded set of bands around it. It is these bands that indicate the exact amount of resistance the component has in interfering with the electrical current it permits to flow through it.
If your blower motor is not functioning and you are trying to determine the faulty part, by looking at the blower motor resistor, you should see it being burnt or partially melted if that is the faulty component on your Chevrolet. If your resistor is in this condition, the reading of the exact amount of resistance it should have by observing the bands around it might not be possible since they could be obscured by the melting of the electrical component. If this is the condition of the resistor on your blower motor, a service manual for your Chevrolet should be consulted.
The danger of placing the wrong blower motor resistor in place is that will permit the incorrect amount of electrical current to flow to the motor. If too much resistance is present, the blower motor will turn at a slower rate than needed. If the resistance is not enough then the electrical blower motor will be burnt out and there will be a need of the entire unit of being replaced.